Establishing the cause of acute vestibular syndrome (AVS) is critical in the first few hours of presentation in the emergency department. The first question to ask is, “is it due to a peripheral vestibular pathology or a stroke?” This is where the head impulse test (HIT) could be very useful. The aims of the study were two-fold: to assess the reliability of the clinical HIT (cHIT) results in differentiating vestibular neuritis (VN) from posterior circulation stroke (PCS) in AVS and to see if video HIT (vHIT) measurements yielded additional information in making the differentiation. Forty patients were included in this prospective study. After detailed bedside neuro-otological examination including the HINTS test, an emergency department specialist and a neurologist made independent diagnosis of whether the ACS was due to a peripheral or central pathology without knowledge of the patients’ history. All patients had vHIT (the results were assessed by an experienced neuro-otologist who was not the tester) and DWI MRI reported by a neuro-radiologist. Twenty-nine controls did not have MRI. The final diagnosis made on the basis of MRI findings was then compared with the clinical diagnosis of the two experts.
The final diagnosis in 24 patients was VN, of these cHIT was assessed as abnormal in 19 (80%) by the emergency specialist and in 20 (83%) by the neurologist. Four patients who were found to have clinically normal cHIT by the neurologist had unilateral low gain and gain asymmetry on vHIT and normal DWI making the final diagnosis VN. Sixteen patients had a central cause for the AVS and in all both experts elicited normal cHIT, an excellent conformity of 0.86 (κ coefﬁcient).
As expected VN patients had ipsilateral and contralateral low gain on vHIT compared to controls. When the vHIT gain and asymmetry in controls were compared with PICA-AICA stroke, the gain was low for the latter but there was no asymmetry. However, there were no significant differences in gain and asymmetry between controls and PICA-SCA strokes. The authors conclude that cHIT “seems adequate in diagnostic evaluation AVS. If vHIT is undertaken, then both gain and gain asymmetry should be taken in account”. This study adds to what is currently known about the relevance of HIT in AVS.